[Xen-devel] [PATCH] credit2: Fix tasklets

[George Dunlap <george.dunlap@xxxxxxxxxxxxx>]

diff -r c7e9f1b99b22 -r befe7b31b451 xen/common/sched_credit2.c
--- a/xen/common/sched_credit2.c        Mon May 10 09:27:17 2010 +0100
+++ b/xen/common/sched_credit2.c        Tue May 11 15:55:27 2010 -0500
@@ -920,16 +920,13 @@
     /* Update credits */
     burn_credits(rqd, scurr, now);
 
-    /* Tasklet work (which runs in idle VCPU context) overrides all else. */
-    if ( !tasklet_queue_empty(cpu) )
-    {
-        snext = CSCHED_VCPU(idle_vcpu[cpu]);
-        goto out;
-    }
-
     /*
      * Select next runnable local VCPU (ie top of local runq).
      *
+     * If there's tasklet work to do, we want to chose the idle vcpu
+     * for this processor, and mark the current for delayed runqueue
+     * add.
+     *
      * If the current vcpu is runnable, and has higher credit than
      * the next guy on the queue (or there is noone else), we want to run him 
again.
      *
@@ -940,7 +937,7 @@
      * If the current vcpu is not runnable, we want to chose the idle
      * vcpu for this processor.
      */
-    if ( list_empty(runq) )
+    if ( list_empty(runq) || !tasklet_queue_empty(cpu) )
         snext = CSCHED_VCPU(idle_vcpu[cpu]);
     else
         snext = __runq_elem(runq->next);
@@ -948,9 +945,10 @@
     if ( !is_idle_vcpu(current) && vcpu_runnable(current) )
     {
         /* If the current vcpu is runnable, and has higher credit
-         * than the next on the runqueue, run him again.
+         * than the next on the runqueue, and isn't being preempted
+         * by a tasklet, run him again.
          * Otherwise, set him for delayed runq add. */
-        if ( scurr->credit > snext->credit)
+        if ( tasklet_queue_empty(cpu) && scurr->credit > snext->credit)
             snext = scurr;
         else
             set_bit(__CSFLAG_delayed_runq_add, &scurr->flags);
@@ -997,7 +995,6 @@
         snext->vcpu->processor = cpu; /* Safe because lock for old processor 
is held */
     }
 
- out:
     /*
      * Return task to run next...
      */

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